In order to advance energy-conservation in the power control of an automobile, a railway car, industrial equipment, and home electric appliances, etc., from the viewpoint of recent environmental and energy problems, higher performance is required of power-electronics equipment. For these power-electronics equipment, use has so far been made of silicon (hereinafter abbreviated as “Si”), as a power semiconductor-material, however, there has started a proposal to use a new power semiconductor-material, such as silicon carbide (hereinafter abbreviated as “SiC”), gallium nitride (hereinafter abbreviated as “GaN”), and diamond, etc., as a method for realizing further energy-conservation. These new power semiconductor-materials each had a problem in that the new power semiconductor-material was a material high in hardness, and fragile, as compared with SiC, being therefore regarded as the difficult-to-machine material.
There is available a catalyst-supported chemical machining method described in PTL 1, and PTL 2, respectively, as a conventional art whereby the respective surfaces of these difficult-to-machine materials are efficiently smoothed.
The method described in PTL 1 is a method whereby a workpiece is disposed in solution of an oxidizer, and a catalyst made of a transition metal is caused to approach the worked surface of a workpiece or come into extreme proximity thereto to thereby remove or elute a compound formed due to a chemical reaction occurring between an active species having high oxidizability, having occurred on the surface of the catalyst, and an atom on the surface of the workpiece to machine the workpiece. It is described in PTL 1 that an abrasive board is used the whole or a part of which is made up of the transition metal as a working example of this method.
The method described in PTL 2 is a method whereby a workpiece composed of GaN, and SiC, etc., is disposed in a process liquid in which a molecule containing a halogen, such as hydrofluoric acid, etc., is dissolved, and a catalyst and the workpiece are caused to undergo relative displacement, while rendering the catalyst made of molybdenum or a molybdenum compound to come into contact with the worked surface of the workpiece or to be in extreme proximity thereto, thereby machining the worked surface of the workpiece. In PTL 2, there is described use of a catalyst board composed of molybdenum or the molybdenum compound as a working example of this method.
Further, the method described in either of PTL 1 and PTL 2 is a method for polishing with the use of only the active species occurred from the oxidizer without using an abrasive grain.